1. Field of the Invention
The present invention relates to optical position sensor systems generally and, more particularly, but not by way of limitation, to a novel infrared optical position sensor system which may be employed to determine the position of an occupant of a vehicle and to disable an air bag restraint if it is determined that the occupant may be injured by deployment of the air bag restraint.
2. Background Art
While the present invention is described, for illustrative purposes, as being applied to occupant classification and position detection in a vehicle, it will be understood that it can be employed in any optical receiver system in which optical image quality is not important.
Inflatable restraints, or air bags, are increasingly being used in vehicles to protect an occupant of a vehicle in case an accident occurs. Typically, a control system senses the occurrence of an accident and causes the air bag to deploy to protect the occupant from colliding with the windshield or dashboard, for example, of the vehicle. An occupant proximity sensor system may comprise part of the control system. Such a system monitors the position of the occupant of the front-outboard passenger seat and automatically, without any action required of the driver or the passenger, determines whether to suppress deployment or allow deployment of the front air bag (and perhaps the side air bag also, if the vehicle is so equipped) applicable to this position. The determination whether or not to suppress air bag deployment is made based on the occupant being in the "at-risk" zone or on classifying the occupant as being in a rear-facing infant seat (RFIS). Conversely, the system allows air bag deployment for a properly seated occupant, i.e., seated with hips back, rearward on the seat cushion and with back resting on the seat back, outside of the at-risk zone.
Upon determining the position/classification of the occupant of the front-outboard seat, the system sends a signal to the sensing and diagnostic module indicating whether to suppress or allow air bag deployment. The system also sends a signal to a display indicating whether the air bag is in a suppressed or an enabled state. If the air bag is in a suppressed state, the signal alerts the driver or passenger to take corrective action, if desirable.
There are many kinds of sensor systems under development. So far, there are mainly two kinds of occupant position sensors: infrared- and ultrasonic-based sensors. Compared to the ultrasonic sensor, the infrared sensor has the fastest response time. An infrared occupant position sensor can classify and recognize an occupant in less than 10 milliseconds.
The typical infrared occupant position sensor has two main elements: an emitter and a receiver. The emitter is a light source that radiates infrared light and illuminates target objects. The receiver consists of an optical system and a detector. The optical system collects light from the target objects and focuses the light signal on the detector. In most such applications, the scattering signal is very weak.
The common requirement for the receiver/optical system is to receive more light and ensure that the spot size on the detector is sufficiently small to allow the optical system to produce the required image quality. Unfortunately, in most cases the scattering light is very weak. In addition, the size of the detector is limited and a highly efficient use of detectors is required. An effective receiver optical system should have a large aperture, short focal length, and large field of view. Unfortunately, a major disadvantage of known such optical systems is complexity and a concomitant prohibitively high cost.
Accordingly, it is a principal object of the present invention to provide an infrared vehicle occupant position detection system for classifying and determining the position of a vehicle occupant that is highly accurate and reliable.
It is a further object of the present invention to provide such a vehicle occupant position detection system that is economical to construct.
It is an additional object of the present invention to provide such a vehicle occupant position detection system that has a large aperture, a short focal length, and a large field of view.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.